Conventionally, systems in which a plurality of apparatuses share a disk storing therein an Operating System (OS) program, application programs, and the like are known. In such a system, the plurality of apparatuses access the disk to use the OS program and the application programs.
Further, another system is also known in which, if one or more of a plurality of apparatuses access a first disk with access frequency that exceeds a threshold value, control is exercised so that the entirety of the storage contents of the first disk is copied onto the second disk and so that the one or more apparatuses of which the frequency of accesses to the first disk exceeds the threshold value are arranged to access the second disk. For example, refer to Japanese Laid-open Patent Publication No. 2004-78999, Japanese Laid-open Patent Publication No. 2004-005634, and Japanese Laid-open Patent Publication No. 07-056691.
According to the conventional technique described above, however, a problem remains where the Input/Output (I/O) load on the first disk is still large.
For example, in the system described above, the entirety of the storage contents of the first disk is copied onto the second disk, after the frequency of accesses to the first disk has exceeded the threshold value. In other words, the control to reduce the access load is exercised after the access load on the first disk has exceeded the predetermined level of load. Thus, in the system described above, the I/O load on the first disk is large before the control to reduce the access load is exercised.
Further, in the system described above, because the entirety of the storage contents of the first disk is copied onto the second disk, after the access load on the first disk has already become large, the I/O load on the first disk becomes even larger from the copying.
The same problem is also observed in the system in which a plurality of apparatuses access a shared volume storing therein an OS program, application programs, and the like. In other words, the problem is observed where the I/O load on the shared volume is large, because the plurality of apparatuses access the shared volume.